Carbon Fiber Polymer Matrix Composites Research Articles

A review to elucidate the multi-faceted science of the electrical-resistance-based strain/temperature/damage self-sensing in continuous carbon fiber polymer-matrix structural composites

A review to elucidate the multi-faceted science of the electrical-resistance-based strain/temperature/damage self-sensing in continuous carbon fiber polymer-matrix structural composites

Reinforced Structure Effect on Thermo-Oxidative Stability of Polymer-Matrix Composites: 2-D Plain Woven Composites and 2.5-D Angle-Interlock Woven Composites.

The thermo-oxidative stability of carbon fiber polymer matrix composites with different integral reinforced structures was investigated experimentally and numerically. Specimens of 2-D plain woven composites and 2.5-D angle-interlock woven composites were isothermally aged at 180 °C in hot air for various durations up to 32 days. The thermal oxidative ageing led to the degradation of the matrix and the fiber/matrix interface. The degradation mechanisms of the matrix were examined by ATR-FTIR and thermal analysis. The interface cracks caused by thermal oxidative ageing were sensitive to the reinforced structure. The thermo-oxidative stability of the two composites was numerically compared in terms of matrix shrinking and crack evolution and then experimentally validated by interlaminar shear tests.

Characterization of cure residual strain development and associated structural distortion in carbon fiber polymer matrix composites

A comprehensive experimental methodology has been developed to measure the in situ cure residual strain (CRS) generation in carbon fiber reinforced polymer (CFRP) laminates using embedded fiber Bragg grating (FBG) sensors. In order to delineate the effect of anisotropy, heterogeneity, laminate thickness and geometry, in situ CRS is measured in pristine epoxy, uni-directional (UD)-CFRPs, multi-directional (MD)-CFRPs and L-shaped MD-CFRP laminates. In this study, emphasis is laid on quantifying the variation in CRS magnitudes as a function of laminates lay-up sequence and thickness. Calibration of FBG sensors are carried out by following well established procedures. Structural distortion due to CRS is correlated using embedded FBG sensor and measured using the coordinate measurement machine (CMM). The presented results show a uniform CRS development across the thickness in MD-CFRP laminates as compared to L-shaped MD-CFRP laminates.

WITHDRAWN: Electret behavior and electret-based self-powering and self-sensing performance of carbon fiber polymer-matrix and carbon-matrix structural composites

WITHDRAWN: Electret behavior and electret-based self-powering and self-sensing performance of carbon fiber polymer-matrix and carbon-matrix structural composites

Effect of fiber lay-up configuration on the electromagnetic interference shielding effectiveness of continuous carbon fiber polymer-matrix composite

Continuous carbon fiber polymer-matrix multifunctional structural composites capable of electromagnetic interference (EMI) shielding are needed for electronics and radiation sources. The laminate's fiber lay-up configuration affects the shielding effectiveness, as shown in this work for unmodified conventional carbon fiber polymer-matrix composite laminates with high-strength PAN-based carbon fiber and a polyamide thermoplastic matrix. The radiation is normal-incidence unpolarized plane wave, as commonly used. The shielding is dominated by absorption rather than reflection – more so for crossply composites than unidirectional composites. Due to the electrical conductivity longitudinal-to-transverse ratio of 930 for a lamina, the absorption-loss/thickness longitudinal-to-transverse ratio is 30 at 1.0 GHz. This factor of 30 means that the contribution of the fibers transverse to the electric field to absorption is negligible compared to that of the fibers parallel to the electric field. The ratio of absorption-loss/thickness for the crossply composite to that for the unidirectional composite with the same number of laminae is ∼4, and the ratio of the reflection loss for the crossply composite to that for the unidirectional composite is ∼2. The values of these ratios are consistent with electromagnetic theory for unpolarized radiation. This work strengthens the science base for the design of continuous fiber composites for shielding.

First report of capacitance-based self-sensing and in-plane electric permittivity of carbon fiber polymer-matrix composite

Capacitance-based damage self-sensing and the in-plane electric permittivity of continuous carbon fiber polymer-matrix composite are unprecedentedly reported. Capacitance-based self-sensing is advantageous over previously reported electrical-resistance-based self-sensing in not needing intimate electrical contacts and that two (rather than four) contacts suffice. Using a 220 × 220-mm2 unidirectional one-lamina polyamide-6-matrix composite, the capacitance (2 kHz) is measured in the through-thickness and in-plane directions using 25 × 25-mm2 aluminum-foil electrodes that are sandwiching and coplanar, respectively. Due to the composite's conductivity and the LCR meter's limitation, a dielectric film (adhesive tape) is positioned between electrode and specimen. In practice, this film can be the paint on the composite. Judiciously positioned artificial damage (1.1-mm diameter through-holes) causes the through-thickness capacitance to increase monotonically and the in-plane capacitance to decrease monotonically with increasing damage, due to the effect of the damage on the fringing electric field. The relative permittivity is 2160 ± 510 and 1640 ± 330 for the longitudinal and transverse directions, respectively, with anisotropy 1.3. The DC resistivity is 0.0072 ± 0.0004 and 10.9 ± 0.9 Ω cm in the longitudinal and transverse directions, respectively, with anisotropy 1500. The conductivity controls the current spreading, while the high permittivity provides the capacitance effect. The resistivity anisotropy causes the dependence of the capacitance-based sensing on the fiber orientation.

Non-destructive infrared inspection of dry multilayer carbon fibre preforms

Thermography was used for performing non-destructive inspection of dry carbon fibre textile preforms used in manufacturing carbon fibre polymer-matrix composites (CF-PMCs). The aim was to probe the feasibility of identifying defects in thick carbon fibres preforms made from multiple layers of industrial textile reinforcements, before composites are manufactured. Inspecting dry preforms will not replace the inspection of final CF-PMC parts but it can avoid costly and wasteful manufacturing of CF-PMC parts from defective preforms, as the defects sought in this paper cannot be observed by visual inspection. The preforms tested were made of two or four layers of industrial carbon fibre textile reinforcements. They featured defects of different widths, types and orientations. Results show that thermography can identify defects in preforms successfully, and that detection is influenced by the orthotropic thermal conductivity of carbon fibres, by yarn and fabric architecture, by the relative orientations of defects and yarns, and by the number of layers.

The effects of defects on the compressive response of thick carbon composites: An experimental and computational study

The effects of defects on lowering the compressive strength of thick unidirectional carbon fiber polymer matrix composites are reported here. Experimental results on specimens with specially designed defect shape and sizes are presented. A decrease in compressive strength is seen with an increase in both misalignment angle and defect height. Defect aspect ratio seems to influence the dominant mode of failure, with lower defect aspect ratio coupons showing propensity to kink, whereas, higher aspect ratio defects showing propensity to split. However, there is no clear demarcation between the two modes or sequence of failure that can be inferred from the test results. To study the interaction and influence of defect dimensions on the compressive strength, a finite element based mechanics model is implemented. The model allows for kinking and splitting of composite layers. This study shows that compressive strength is dependent not only on the geometry of defects but also on the consolidation of plies over the defect. Furthermore, the need to have a mechanism based notion of compressive strength is borne out of the test results and model predictions.

Effect of thermo-oxidative aging on compressive behavior of carbon fiber polymer matrix composites

The effects of reinforcement architecture on the compressive behaviors of carbon fiber polymer matrix composites (CF-PMCs) under thermo-oxidative aging conditions were investigated. Samples of three-dimensional and four-directional braided carbon fiber/epoxy composites (BC) and laminated plain woven carbon fiber/epoxy composites (LC) were subjected to isothermal aging at 80℃, 100℃, 120℃ and 140℃ in air circulating ovens for various durations up to 1200 h. The process resulted in progressive deterioration of the matrix reins and fiber/matrix interfaces, in the form of chain scissions, weight loss and fiber/matrix debonding, which significantly led to the decrease of the compressive strength. In addition, the compressive strength retention rates of BC were higher than those of LC at the same aging conditions due to the differences of their reinforcement architecture. On the one hand, LC lost more weight than BC because the percentage of exposure of fiber ends to air in the LC samples was five times more than that in the BC samples. Moreover, the BC samples could resist the compressive load as an integral structure and did not show delamination damage as in the case of LC samples, although the resin was damaged and the adhesive force between fiber bundles and resin decreased after thermo-oxidative aging. Therefore, adopting the three-dimensional and four-directional braided preform as the reinforcement of CF-PMCs is an effective way to improve their compressive strength under thermo-oxidative aging conditions.

Approaches to understand and predict the influence of rapid heat-up on degradation and strength of carbon fibre polymer matrix composites

This study focuses on understanding and prediction of short-term thermal degradation of polymer matrix composites. One sided irradiation of two commercial composites (HexPly® 8552/IM7 and M18-1/G939) is carried out on specimens of various thickness (2, 4, 6 mm) at different heat fluxes (50 and 80 kW/m2) for various exposure times prior to ignition. The aim is to correlate the amount of the applied thermal energy with the heat damage and the residual mechanical strength. Among the two primary components of each matrix the epoxy resin is observed to degrade faster than the thermoplastic under thermal load, as measured by IR spectroscopy. A correlation is achieved between the interlaminar shear strengths and the relative amount of the residual matrix components. The interlaminar shear strengths and degradation processes are assessed in dependence of the applied energy per volume. The derived relationships and a chemometric analysis of IR spectra, can be used to rapidly estimate mechanical properties, as well as other properties of specimens with unknown thermal preload. Degradation processes are discussed in detail.

Continuous carbon fiber polymer–matrix composites in unprecedented antiferroelectric coupling providing exceptionally high through-thickness electric permittivity

Continuous carbon fiber polymer–matrix composites in unprecedented antiferroelectric coupling, as enabled by stacking composites with positive value (up to 400) and negative value (down to −600) of the electric permittivity, provide exceptionally high through-thickness permittivity up to 78,000 (≤2.0 MHz), corresponding to a capacitance of 370 μF/m2. The high capacitance is consistent with the equation for negative and positive capacitors in series. The permittivity tailoring of the composites involves dielectric cellulosic tissue paper interlaminar interlayers. Negative permittivity (not previously reported for carbon fiber composites) requires the paper to be wet with tap water (resistivity 1.5 kΩ cm) during incorporation in the composite, though the water evaporates and leaves ions at very low concentrations during composite fabrication, and also requires optimum through-thickness resistivity (e.g., 1 kΩ cm, as given by paper thickness 35 μm); it is probably due to interactions between the functional groups on the carbon fiber surface and the residual ions (mainly chloride) left after tap water evaporation.

Thermal and mechanical properties of carbon fiber polymer-matrix composites with a 3D thermal conductive pathway

The low through-thickness thermal conductivity limits the thermal management application of carbon fiber reinforced polymer-matrix (CFRP) composites. A simple method of constructing a 3D thermal conductive pathway is developed to improve the through-thickness thermal conductivity of CFRP laminated composites. Then, a z-filler laminated composite panel is fabricated by filling the copper spheres and coating the aluminum foils, and its effective thermal conductivity is investigated, both experimentally and theoretically. Analytical predictions agree well with measured values. The through-thickness thermal conductivity of z-filler laminated composites has been significantly improved by increasing the z-filler volume fraction but by decreasing the interface thermal resistance. A maximum improvement in the through-thickness thermal conductivity is up to approximately 12 times compared with the unmodified composite materials. Moreover, with high through-thickness thermal conductivity, z-filler laminated composites possess both low coefficient of thermal expansion (CTE) and adequate mechanical properties for structural applications. Thus, z-filler laminated composites can be considered as promising candidates for multifunctional material in the high-end heat dissipation fields.

High-fidelity micro-scale modeling of the thermo-visco-plastic behavior of carbon fiber polymer matrix composites

An experimentally validated micro-scale analysis of the visco-thermo-mechanical behavior of polymer matrix composites under different loads is proposed. A new constitutive law for the matrix material is developed taking into account the pressure dependence of the material as well as strain-rate and temperature dependence. Capturing the matrix behavior under multi-axial stress states is concluded to be essential to accurately predict the composite material behavior, even when considering simple load cases such as transverse compression and/or shear. Without any calibration procedure at the composite level, good agreement with the experimental data is observed for different loading conditions, including strain-rate dependency.Using this validated micro-scale model, a three-dimensional simulation of the formation of a kink band under longitudinal compression of the composite is conducted. A new evidence at micro-scale is found supporting the hypothesis that shear stresses transferred between fibers and matrix are particularly important in the formation of the kink band.

The effect of reinforced structure on thermo-oxidative stability of polymer-matrix composites

A new concept in improving the thermo-oxidative stability of carbon fiber polymer-matrix composites (CFPMCs) by adopting integral reinforced structure was investigated. Specimens of three-dimensional and four-directional braided carbon fiber/epoxy composites (BC) and laminated plain woven carbon fiber/epoxy composites (LC) were subjected to isothermal aging at 90℃, 120℃, and 150℃ in air circulating ovens for various durations up to 13 days. The process resulted in progressive deterioration of the matrix reins and fiber/matrix interfaces, in the form of chain scissions, weight loss, and fiber/matrix debonding, which significantly led to the decrease of the flexural strength. Besides, the flexural properties’ retention rates of BC were higher than those of LC at the same aging conditions due to the difference of the reinforced structures. On the one hand, LC lost more weight than that of BC because the percentage of fiber ends area exposure to air in LC specimen was three times more than that in BC specimen. On the other hand, the BC specimens can resist the flexural load as an integral structure although the resin was damaged and the adhesive force between fiber bundles and resin decreased after thermo-oxidative aging, and no delamination happened like the LC specimens. Therefore, adopting three-dimensional and four-directional braided preform as the reinforcement of CFPMCs is an effective way to improve their thermo-oxidative stability.

79 Experimental Assessment of Single and Cumulative Impact Damage in Carbon Fiber Polymer Matrix Composites Using Electrical Resistance Measurements

79 Experimental Assessment of Single and Cumulative Impact Damage in Carbon Fiber Polymer Matrix Composites Using Electrical Resistance Measurements

Experimental Assessment of Single and Cumulative Impact Damage in Carbon Fiber Polymer Matrix Composites Using Electrical Resistance Measurements

In this work the impact damage sensing capabilities in AS4/3501-6 carbon fiber polymer matrix composites are investigated. A fully instrumented experimental setup for characterization of electrical properties has been developed. The one-dimensional electrical resistance method was employed for damage sensing. 16-ply [0/45/–45/90] 2s and 32-ply [0/45/–45/90] 4s laminates were tested. Single impact and cumulative low velocity impact studies were conducted and electrical resistance measurements were performed to assess damage. The results show that the one-dimensional electrical resistance technique had a limited success at sensing impact damage in AS4/3501-6 composites due to low initial resistances of the composites tested. doi:10.12783/issn. 2168-4286/2.2/Zhupanska

Through-thickness piezoresistivity in a carbon fiber polymer-matrix structural composite for electrical-resistance-based through-thickness strain sensing

Piezoresistivity (change of the volume electrical resistivity with strain) in continuous carbon fiber polymer-matrix structural composites allows electrical-resistance-based strain/stress sensing. Uniaxial through-thickness compression is encountered in fastening. As shown for a 24-lamina quasi-isotropic epoxy-matrix composite, compression results in (i) strain-induced reversible decreases in through-thickness and longitudinal volume resistivities, due to increase in the degree of through-thickness fiber–fiber contact, and (ii) minor-damage-induced irreversible changes in these resistivities, due to a microstructural change involving an irreversible through-thickness resistivity increase and an irreversible longitudinal resistivity decrease. The Poisson effect plays a minor role. The effects in the longitudinal resistivity are small compared to those in the through-thickness direction, but longitudinal resistance measurement is more practical. The through-thickness gage factor (reversible fractional change in resistance per unit strain) ranges from 2.6 to 5.1 and the reversible fractional change in through-thickness resistivity per unit through-thickness strain ranges from 1.5 to 4.0, both quantities decreasing with increasing strain magnitude from 0.19% to 0.73% due to the increasing irreversible effect. The irreversible fractional change in through-thickness resistivity per unit through-thickness strain ranges from −1.0 to −1.3 and is strain independent. The effects are consistent with the surface resistance changes previously reported for the same material under flexure.

Carbon materials for structural self-sensing, electromagnetic shielding and thermal interfacing

This paper reviews carbon materials for significant emerging applications that relate to structural self-sensing (a structural material sensing its own condition), electromagnetic interference shielding (blocking radio wave) and thermal interfacing (improving thermal contacts by using thermal interface materials). These applications pertain to electronics, lighting (light emitting diodes), communication, security, aircraft, spacecraft and civil infrastructure. High-performance and cost-effective materials in various forms of carbon have been developed for these applications. The forms of carbon materials include carbon fiber, carbon nanofiber, exfoliated graphite, carbon black and composite materials. Short carbon fiber cement-matrix composites and continuous carbon fiber polymer-matrix composites are particularly effective for structural self-sensing, with the attributes sensed including strain, stress, damage and temperature. Flexible graphite as a monolithic material and nickel-coated carbon nanofiber as a filler are particularly effective for electromagnetic shielding. Carbon black paste, graphite nanoplatelet paste and flexible graphite (filled with carbon black paste) are particularly effective for thermal interfacing; carbon nanotube arrays are less effective than these pastes. The associated science pertains to the relationship among processing, structure and properties in relation to the abovementioned applications. The criteria behind the design of materials for these applications and the mechanisms of the associated phenomena are also addressed.

Increasing the through-thickness thermal conductivity of carbon fiber polymer–matrix composite by curing pressure increase and filler incorporation

The low through-thickness thermal conductivity limits heat dissipation from continuous carbon fiber polymer–matrix composites. This conductivity is increased by up to 60% by raising the curing pressure from 0.1 to 2.0 MPa and up to 33% by incorporation of a filler (⩽1.5 vol.%) at the interlaminar interface. The 7-μm-diameter 7-W/m K-thermal-conductivity continuous fiber volume fraction is increased by the curing pressure increase, but is essentially unaffected by filler incorporation. The thermal resistivity is dominated by the lamina resistivity (which is contributed substantially by the intralaminar fiber–fiber interfacial resistivity), with the interlaminar interface thermal resistivity being unexpectedly negligible. The lamina resistivity and intralaminar fiber–fiber interfacial resistivity are decreased by up to 56% by raising the curing pressure and up to 36% by filler incorporation. The curing pressure increase does not affect the effectiveness of 1-mm-long 10-μm-diameter 900–1000-W/m K-thermal-conductivity K-1100 carbon fiber or single-walled carbon nanotube (SWCNT) as fillers for enhancing the conductivity, but hinders the effectiveness of carbon black (CB, low-cost), which is less effective than K-1100 or SWCNT at the higher curing pressure, but is almost as effective as K-1100 and SWCNT at the lower curing pressure. The effectiveness for enhancing the flexural modulus/strength/ductility decreases in the order: SWCNT, CB, K-1100.

The Research of Modified Carbon Fiber Polymer-Matrix Composites Properties of the Mechanism of Piezoresistivity

At present, the study of smart composite material of carbon fiber is mainly focused on the usage of the material pressure-resistant effect. The change of resistance reflects the force status of the structure and its performance mainly depends on the sensitivity of pressure-resistantance. Such composite’s sensitivity has a relationship with the sample preparation process. In this paper, the resin-based carbon fiber is improved so as to obtain a high sensitivity and good stability bundle of modified carbon fiber polymer-matrix composites. Clamp the samples of this material on the micro-tensile test table, the characteristics of mechanism pressure-resistant is analyzed by observing the fiber interface changes through SEM when loaded, combined with monotonic loading curve of the sample. With the electrical model of parallel circuit and normal distribution model and Weibull model, piezoresistivity model is established. Compared with the model curve and the experimental model, the mode is verified being a high accuracy.